Valve for direct-acting engines



(No Model.) 2 Sheets-Sheet 1. M. T. DAVIDSON.

VALVE FOR DIRECT ACTING ENGINES.

No. 497,442. Patented May 16, 1893.

FT'TI (No Model.) 2 Sheets-Sheet 2. M. T. DAVIDSON.

VALVE FOR DIRECT ACTING ENGINES.

No. 497,442. Patented May 16, 1893.

v I B 2900 a wa awvwwto'z QT M W W UNITED STATES PATENT OFFICE.

MARSHALL T. DAVIDSON, OF BROOKLYN, NEW YORK.

VA LVE FOR DIRECT-ACTING ENGINES.

SPECIFICATION forming part of Letters Patent No. 497,442, dated May 16,1893.

Application filed October 11, 1892. Serial No, 443,486- (No model.)

To all whom it may concern.-

Be it known that I, MARSHALL T. DAVID- SON, a citizen of the UnitedStates, residing at Brooklyn, in the county of Kings and State of NewYork, have invented certain new and useful Improvements in Valves forDirect- Acting Steam-Engines, of which the following is a specification.

My invention relates to direct acting steam engines, adapted moreespecially for operating pumps, and it has for its object to providemeans whereby the valves of such engines may be more readily controlledto operate under varying pressures of steam.

To these ends my invention consists in the various features ofconstruction and arrangement substantially as hereinafter moreparticularly specified.

Referring to the accompanying drawings,

Figure 1, is a longitudinal vertical section through the steam cylinderand valve mechanism connected thereto. Fig. 2, is a vertical transversesection on the lines 2-2, Fig. 1. Fig. 3, is a horizontal sectionthrough the valve mechanism on the lines 3-3, Fig. 1. Fig. 4, is anenlarged detail View showing a throttling device for the ports of thevalve,

and Fig. 5, is a similar view of a modified form of throttling device.

My invention relates to What is generally known in the trade as theDavidson direct acting steam engine, and in the accompanying drawings Ihave illustrated sufficient of this engine to enable those skilled inthe art to understand its construction and operation, and have shown mypresent improvement as applied thereto.

The steam cylinder A, which is shown only partially, is provided withthe piston P, the piston rod P, which may be connected with the pumpingapparatus not shown herein. Mounted on the steam cylinder is the steamchest 0, receiving steam from the pipe B, and containing a valve D. Thisvalve is shown as a D-shaped valve having pistons E, E, which may beformed integral with the valve or connected thereto in any desiredmanner. The under side of the valve is recessed as at f, to form anexhaust port communicating with the main exhaust passage F, formed inthe casing of the steam chest, and the spaces g, 9', between the ends ofthe valve and the pistons operate as ports to communicate with the mainpiston port G, G, of the steam cylinder. The steam chest is alsoprovided with valve piston ports 6, e, which extend longitudinally ofthe steam chest from a point about the center thereof to near theopposite ends, and these valve piston ports are arranged on oppositesides of the lower portion of the steam chest as seen in Figs. 2 and 3,and have openings communicating with the chest at each end. Thearrangement of these ports is best indicated in dotted lines in Fig. 3,and it will be seen that the valve D, is provided with exhaust notchesf, f and steam notches or recesses d, d, in its sides which can bebrought in coincidence with the openings of the valve piston ports.

In the Davidson engine the valve D, is provided with a pin H, whichextends into the exhaust port F, and also mounted in the exhaust port isa cam I, to which is connected the arm I, and this in turn is connectedby suitable mechanism, as alink 1 to the piston rod, so that as thepiston moves, the valve 1), is mechanically oscillated to open and closethe valve piston ports, and is partly thrown longitudinally so as toproduce a closure of the main piston ports, and the further longitudinalmovement of the valve in the steam chest is accomplished by the steampassing through the ports 6, e, and acting on the pistons. Thus it willbe seen that the valve has first an oscillating movement producedmechanically, then a longitudinal or reciprocating movement alsoproduced mechanically, and finally a further longitudinal movementproduced by steam pressure. This operation will be readily understood byreferring to Fig. 1, wherein the parts are shown with the main pistonport G, as partially open to the passage of steam to the steam cylinder,while the port G, is partially open to exhaust from the cylinder, andthe piston is shown in the position near to the end of its stroke, andthe cam I, oscillated the valve and moved it longitudinally, so as tonearly close the steam passages, and, as the piston advances farther,these passages will be completely closed by the mechanical action of thecam. The oscillation of the valve has in the meantime opened the valvepiston port e, so that the steam will pass behind the valve piston E,and at the same time the valve piston port (2, has been opened, so as toexhaust from the steam chest in front of the valve piston E, and it willbe readily understood that under these conditions the valve will bethrown over to its fullest extent by the direct pressure of the steam,and the main piston port G, will be opened for steam, and the port G, toexhaust.

So far the construction is the usual construction of the Davidson pump,and it has been found that under proper conditions this construction isfully operative in a satisfactory manner. It happens, however, inpractice that pumps so constructed are used under varying conditions ofsteam pressure, and while the pump will operate satisfactorily under agiven pressure, if the same pump is subjected to a greatly increasedpressure, the action of the steam on the valve pistons will move thevalve too rapidly, causing a thumping or pounding of the valves of theengine and pump which is open to well known objections. In order toovercome these objections, and to provide a pumping engine which isadapted to be used under extreme varying pressures without the necessityof rearranging or changing the parts, is the main object of my presentinvention, and to accomplish this object I provide means whereby thevalve piston ports may be throttled, so that the passage of steam to theends of the steam chest and its action upon the valve pistons can bequickly and readily regulated and adjusted to meet the requirements ofany particular case. I accomplish this by providing a throttling plug K,which is arranged in the present instance in the end of the steam chest0, and is provided with a screw stem is, passing through the bearing K,and extending into the valve piston port 6, or e, and controlling thepassage of the steam into the steam chest behind the pistons. Thus itwill be seen, that, if the engine is operating under too high pressureof steam, which would produce pounding or too rapid movement of thevalve, by properly adjusting the plug K, the passage of the steam intothe chest behind the piston can be regulated by the plug, so'

that the valve will be moved in the proper and desired manner bythesteam pressure on the piston thereof.

In Fig. 5, I have shown another arrangement of the plug K, in which theplug is fitted on the end of the screw K turning in bearings in the headof the steam chest, andacap K is shown which fits over the screw toprotect it after being properly adjusted.

I have further found that when the valve is operated by the cam, owingto the steam remaining in the steam chest at the end of the valve pistonwhere it has just exerted its pressure to complete the movement of thevalve, considerable force is required to move the valve in the oppositedirection against this steam, it acting somewhat as a cushion not havingtime to condense, and consequently opposes the return movement of thevalve. More than this, as the valve progresses in its movement under theaction of the cam before the exhaust port is opened behind it, theresistance increases owing to the increased compression of the steam, bythe space itoccupies being reduced, and as a consequence there is moreor less wear upon the cam, and wasting of steam power to produce thefirst movement of the cam by mechanical means, and it is the furtherobject of my invention to overcome and obviate this objection. In orderto accomplish this result I provide the steam chest with a valve pistonexhaust, and arrange it to be controlled by the valve piston, so that ator about the moment the valve piston reaches the end of itsreciprocation in either direction it shall open the exhaust in the rearof the piston, and allow the steam to escape and prevent its acting as acushion, or exerting back pressure against the movements of the 5 valve.This is readily accomplished in the construction shown by extending thevalve piston ports e, e, as shown at 6 a, respectively, and having thecorresponding openings e e into the steam chest arranged so that as soonas the valve piston is completely thrown, the port will be opened toexhaust, and this is clearly indicated in Fig. 3, of the drawings andneed not be particularly described, as those skilled in the art willreadily understand its operation in connection with the abovedescription. It will thus be seen that I avoid moving the valve againstthe pressure of the steam in the end of the steam chest which has beenused to move the valve in the opposite direction, and thereby thefriction of the parts and resistance to be overcome by the cam aregreatly reduced, enabling the valve to operate freely and quickly.

\Vhat I claim is 1. In a direct acting engine, the combination with avalve having an oscillating and longitudinal movement by mechanicalmeans, and a further longitudinal movement by steam pressure, of meansfor throttling the steam producing said longitudinal movement,substantially as described.

2. In a direct acting engine, the combination with a steam chest havingsteam ports extending from the center to the ends of the chest and beingfurther provided with exhaust ports extending from the center of thechest to the rear of the valve; of a valve arranged to be oscillated andmoved mechanically a portion of its distance and to open the steam portsto allow it to be moved a farther distance, and to further open theexhaust ports when the valve has moved to the end of its reciprocation;substantially as described.

3. In a pumping engine, the combination with a steam chest having steamports e,-e and exhaust ports 8 6 extending from the steam ports; of avalve having pistons mount- I0 ed in the chest and arranged to controlthe steam and exhaust ports; substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

MARSHALL T. DAVIDSON.

Witnesses:

WALTER E. CLARKE, WM. A. DREWETT.

